J/A+A/603/A22ivo://CDS.VizieR/J/A+A/603/A22doi:10.26093/cds/vizier.36030022CDSZeng S.Jimenez-Serra I.Cosentino G.Viti S.Barnes A.T.,Henshaw J.D.Caselli P.Fontani F.Hily-Blant P.2018-06-06T05:24:24Z2017-07-03T08:14:43ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frinterstellar-mediummolecular-cloudsspectroscopyWe present the results of the measurement of nitrogen fractionation in a sample of infrared-dark clouds (IRDCs) cores which are believed to be the precursors of high-mass stars and star clusters. We observed the J=1-0 transitions of HCN, H^13/^CN, HC^15/^N, HN^13/^C, and H^15/^NC towards a sample of 22 cores in four IRDCs using the IRAM 30m telescope.Assuming LTE and a temperature of 15K, the 14N/^15/^N ratios measured are consistent with the terrestrial atmosphere(TA) and protosolar nebula(PSN) values, and with the ratios measured in low-mass prestellar cores. However, the 14N/^15/^N ratios measured in cores C1, C3, F1, F2, and G2 do not agree with the results from similar studies towards the same cores using nitrogen bearing molecules with nitrile functional group(-CN) and nitrogen hydrides (-NH) although the ratio spread covers a similar range. Relatively low 14N/^15/^N ratios amongst the four-IRDCs were measured in IRDC G which are comparable to those measured in small cosmomaterials and protoplanetary disks. The low average gas density of this cloud suggests that the gas density, rather than the gas temperature, may be the dominant parameter influencing the initial nitrogen isotopic composition in young PSN.2017A&A...603A..22Zhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/603/A22CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/603/A22https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/603/A22http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/603/A22https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/603/A22https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/603/A22http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/603/A22GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/603/A22/list (List of spectra)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/603/A22/list?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/603/A22/list?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/603/A22/list?GETtext/xml+votable180.050000true280.68933-4.06920.005555555555555556Associated datahttps://cdsarc.cds.unistra.fr/assocdata/?obs_collection=J/A+A/603/A226/30256 30258 30318-30319https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/603/A22?format=asciidefaultJ/A+A/603/A22/listList of spectrarecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000Right Ascension of center (J2000)degpos.eq.ra;meta.mainDEJ2000Declination of center (J2000)degpos.eq.dec;meta.mainNxNumber of pointsmeta.numberintObs.DateObservation date (YYYY-MM-DDThh:mm:ss.sss)time.epoch;obscharbFreqLower value of frequency intervalHzem.freq;stat.mindoubleBFreqUpper value of frequency intervalHzem.freq;stat.maxdoubledFreqFrequency resolutionHzspect.resolutionintsizeSize of FITS fileKibytephys.size;meta.fitsintspShow the spectrummeta.ref.urlcharFileNameName of FITS file, in subdirectory spmeta.id;meta.fitscharTitleTitle of the FITS filemeta.title;meta.fitsAssocDataAssociated Data web pagemeta.bib.pagechar